Abstract:
Foresters commonly separate forest floor or down woody materials (DWM) into three successive layers: (1) branches and logs (fine and coarse woody material), (2) litter, and (3) duff. Additionally, live and dead understory shrubs and herbs are included with forest floor measurements. Duff includes the dark, partly decomposed organic material (where ... plant forms are unrecognizable) above mineral soil. On top of duff is litter, which includes recognizable plant parts such as leaves and flowers but not branches. Branches are separated into three size classes of fine woody material (FWM): <6, 6 to 25, and 26 to 76 mm in diameter. These classes correspond to 1-hour, 10-hour, and 100-hour fire fuel classes, respectively. Coarse woody material (CWM) includes all logs >76 mm in diameter and corresponds to the 1000-hour fuel class. The US Department of Agriculture Forest Inventory and Analysis (FIA) program currently measures variables related to DWM on a Phase 3 (P3) subsample of its Phase 2 (P2) plots. We used P3 and P2 FIA data to estimate DWM for all plots in the eastern half of the FIA database. First we acquired, compiled, and computed mass on CWM, FWM, litter, duff, and shrub/herb cover from different data sources, then we developed regression models to predict DWM components for extension to almost 100,000 eastern FIA plots. The models for estimating DWM for all FIA plots produced rather weak correlations to several climate and dead-tree variables, and these results could only be improved with modification of FIA field procedures. Average fuel mass for the eastern US are 6.0, 6.1, 5.3, 9.6, and 1.3 Mg/ha for CWM, FWM, litter, duff, and shrub/herb cover, respectively. The total of all DWM components for the eastern US is approximately 2,000 Tg or 17% of the total forest biomass, which includes 9,000 Tg live and 500 Tg dead biomass in standing trees.

The purpose behind the development of this dataset is a regional-scale estimate of down woody materials that contribute to prescribed and wildland fire fuels. After developing accurate models of down woody materials by fuel class, location, and other forest attributes, we will then link the models to PEcon, a species-level forest growth and economics model, to predict down woody materials and fuel loads in response to changes in climate, land use, species composition, and timber markets.

Chojnacky, D.C., R.A. Mickler, and L.S. Heath Carbon in Down Woody Materials of Eastern U.S. Forests -- {79147633-67E7-4A1C-BD12-4C82F90828FF} Geospatial Data Presentation Form: Conference proceedings Second Annual Conference on Carbon Sequestration. Alexandria, VA, May 2003. This publication is available through the Second Annual Conference on Carbon Sequestration website at http://www.carbonsq.com/ -- pdf file may be downloaded http://www.carbonsq.com/